Our Sun is $2\mathrm{.}3104$ ly $($light$-$years$)$ from the cen$-$

ter of our Milky Way galaxy and is moving in a cir$-$

cle around that center at a speed of $250$ km$/$s$.($a$)$

How long does it take the Sun to make one revolu$-$

tion about the galactic center? $($b$)$ How many revo$-$

lutions has the Sun completed since it was formed

about $4\mathrm{.}5109$ years ago?